Automating string reallocation when it is possible (#2076)

* Automating string reallocation

* Typo

doc/basics.md

@@ -179,8 +179,8 @@ strcpy(json, "[1]");
 ondemand::document doc = parser.iterate(json, strlen(json), sizeof(json));
 ```
 
-The simdjson library will also accept `std::string` instances, as long as the `capacity()` of
-the string exceeds the `size()` by at least `SIMDJSON_PADDING`. You can increase the `capacity()` with the `reserve()` function of your strings.
+The simdjson library will also accept `std::string` instances. If the provided
+reference is non-const, it will allocate padding as needed.
 
 You can copy your data directly on a `simdjson::padded_string` as follows:
 

include/simdjson/generic/ondemand/parser-inl.h

@@ -68,6 +68,13 @@ simdjson_warn_unused simdjson_inline simdjson_result<document> parser::iterate(s
   return iterate(padded_string_view(json, allocated));
 }
 
+simdjson_warn_unused simdjson_inline simdjson_result<document> parser::iterate(std::string &json) & noexcept {
+  if(json.capacity() - json.size() < SIMDJSON_PADDING) {
+    json.reserve(json.size() + SIMDJSON_PADDING);
+  }
+  return iterate(padded_string_view(json));
+}
+
 simdjson_warn_unused simdjson_inline simdjson_result<document> parser::iterate(const std::string &json) & noexcept {
   return iterate(padded_string_view(json));
 }

include/simdjson/generic/ondemand/parser.h

@@ -107,6 +107,8 @@ public:
   /** @overload simdjson_result<document> iterate(padded_string_view json) & noexcept */
   simdjson_warn_unused simdjson_result<document> iterate(const std::string &json) & noexcept;
   /** @overload simdjson_result<document> iterate(padded_string_view json) & noexcept */
+  simdjson_warn_unused simdjson_result<document> iterate(std::string &json) & noexcept;
+  /** @overload simdjson_result<document> iterate(padded_string_view json) & noexcept */
   simdjson_warn_unused simdjson_result<document> iterate(const simdjson_result<padded_string> &json) & noexcept;
   /** @overload simdjson_result<document> iterate(padded_string_view json) & noexcept */
   simdjson_warn_unused simdjson_result<document> iterate(const simdjson_result<padded_string_view> &json) & noexcept;

tests/ondemand/ondemand_parse_api_tests.cpp

@@ -144,14 +144,20 @@ namespace parse_api_tests {
     }
 
     {
-      std::string json = "12";
+      std::string json = "12345642314123421321321321321321312321321321321312";
       json.shrink_to_fit();
       cout << "- string, 0 padding" << endl;
-      ASSERT_ERROR( parser.iterate(json), INSUFFICIENT_PADDING );
+      ASSERT_SUCCESS( parser.iterate(json) );
+    }
+
+    {
+      std::string json = "12345642314123421321321321321321312321321321321312";
+      json.shrink_to_fit();
+      cout << "- string, 0 padding" << endl;
+      ASSERT_ERROR( parser.iterate((const std::string&)json), INSUFFICIENT_PADDING );
       // It's actually kind of hard to allocate "just enough" capacity, since the string tends
       // to grow more than you tell it to.
     }
-
     TEST_SUCCEED();
   }
 

tests/ondemand/ondemand_readme_examples.cpp

@@ -38,6 +38,7 @@ bool to_string_example_no_except() {
 
 #if SIMDJSON_EXCEPTIONS
 
+
 bool to_string_example() {
     TEST_START();
   auto json = R"({
@@ -51,6 +52,7 @@ bool to_string_example() {
   ASSERT_EQUAL(name, "Daniel");
   TEST_SUCCEED();
 }
+
 bool gen_raw1() {
   TEST_START();
   simdjson::ondemand::parser parser;
@@ -171,6 +173,76 @@ bool examplecrt() {
   TEST_SUCCEED();
 }
 
+
+bool examplecrt_realloc() {
+  TEST_START();
+  std::string unpadded_input_json = R"([
+	{ "monitor": [
+		{ "id": "monitor",		"type": "toggle",		"label": "monitor"			},
+		{ "id": "profile",		"type": "selector",		"label": "collection"		},
+		{ "id": "overlay",		"type": "selector",		"label": "overlay"			},
+		{ "id": "zoom",			"type": "toggleSlider",	"label": "zoom"				}
+	] },
+
+	{ "crt": [
+		{ "id": "system",		"type": "multi",		"label": "system",		"choices": "PAL, NTSC"	},
+		{ "type": "spacer" },
+		{ "id": "brightness",	"type": "slider",		"icon": "brightness"		},
+		{ "id": "contrast",		"type": "slider",		"icon": "contrast"			},
+		{ "id": "saturation",	"type": "slider",		"icon": "saturation"		},
+		{ "type": "spacer" },
+		{ "id": "overscan",		"type": "toggleSlider",	"label": "overscan"			},
+		{ "type": "spacer" },
+		{ "id": "emulation",	"type": "toggle",		"label": "CRT emulation"	},
+		{ "type": "spacer" },
+		{ "id": "curve",		"type": "toggleSlider",	"label": "curve"			},
+		{ "id": "bleed",		"type": "toggleSlider",	"label": "bleed"			},
+		{ "id": "vignette",		"type": "toggleSlider",	"label": "vignette"			},
+		{ "id": "scanlines",	"type": "toggleSlider",	"label": "scanlines"		},
+		{ "id": "gridlines",	"type": "toggleSlider",	"label": "gridlines"		},
+		{ "id": "glow",			"type": "toggleSlider",	"label": "glow"				},
+		{ "id": "flicker",		"type": "toggleSlider",	"label": "flicker"			},
+		{ "id": "noise",		"type": "toggleSlider",	"label": "noise"			},
+    {}
+	] }
+])";
+  unpadded_input_json.shrink_to_fit();
+  auto parser = ondemand::parser{};
+  auto doc = parser.iterate(unpadded_input_json);
+  auto root_array = doc.get_array();
+  // the root should be an object, not an array, but that's the JSON we are
+  // given.
+  for (ondemand::object node : root_array) {
+    // We know that we are going to have just one element in the object.
+    for (auto field : node) {
+      std::cout << "\n\ntop level:" << field.key() << std::endl;
+      // You can get a proper std::string_view for the key with:
+      // std::string_view key = field.unescaped_key();
+      // and second for-range loop to get child-elements here
+      for (ondemand::object inner_object : field.value()) {
+        auto i = inner_object.begin();
+        if (i == inner_object.end()) {
+          std::cout << "empty object" << std::endl;
+          continue;
+        } else {
+          for (; i != inner_object.end(); ++i) {
+            auto inner_field = *i;
+            std::cout << '"' << inner_field.key()
+                      << "\" : " << inner_field.value() << ", ";
+            // You can get proper std::string_view for the key and value with:
+            // std::string_view inner_key = field.unescaped_key();
+            // std::string_view value_str = field.value();
+          }
+        }
+        std::cout << std::endl;
+      }
+      // You can break here if you only want just the first element.
+      // break;
+    }
+  }
+  TEST_SUCCEED();
+}
+
 bool number_tests() {
   TEST_START();
   ondemand::parser parser;
@@ -1457,6 +1529,7 @@ bool run() {
     && number_tests()
     && current_location_tape_error_with_except()
     && examplecrt()
+    && examplecrt_realloc()
   #endif
   ;
 }